The field of ink jet printing is replete with references describing solutions to problems associated with placing ink drops on a print media. In particular, color ink jet printing requires careful placement of ink drops to meet print resolution and color fidelity requirements without producing undesired printing artifacts such as banding, streaking, bleeding, puddling, and chroma shifting.
Ink-jet printing systems commonly utilize either direct printing or offset printing architecture. In a typical direct printing system, ink is ejected from jets in the print head directly onto a final receiving medium. In an offset printing system, the print head jets the ink onto an intermediate transfer surface, such as a liquid layer on a drum. The final receiving medium is then brought into contact with the intermediate transfer surface and the ink image is transferred and fused to the final receiving medium.
Many ink jet printers include a control software driver program (hereinafter "printer driver") for handling various aspects of the printing operation. Such printer drivers are often interfaced to a page description language, such as the PostScripts.RTM. language available from Adobe Systems, Inc., Mountain View, Calif. The page description language generates a bit map that represents the image to be printed. The page description language also typically includes methods for manipulating text and graphics, selecting media sizes, types, trays, and the number of copies to be printed.
Ink jet printers generally utilize a single ink dot size for printing an image on a receiving medium. In single dot size printing, the average reflectance of a region of an image is typically modulated by a process referred to as "dithering," in which the perceived intensity of an array of dots is modulated by selectively printing the array at a predetermined dot density. For example, if a 50 percent local average reflectance is desired, half of the dots in the array are printed. A particular type of dithering is digital halftoning, also known as "spacial dithering." Digital halftoning refers to a process of arranging binary picture elements or "pixels" to create the illusion of continuous-tone images.
It is known to utilize image processing techniques to increase printer addressability and thereby enhance resolution. However, the prior art techniques for increasing resolution have generally required reducing ink drop size, increasing the number of jets on the print head, increasing the jet firing rate (the number of drops ejected per second) and/or increasing overall print time. The smaller drop requirement can be mitigated by removing selected ink drops from the interior of solid fill shapes, including text and thick lines. This process, often referred to as decimation, preserves the smoothness of the edges of the solid filled shapes without requiring excessive ink. However, decimation still results in increased print time for a print head with a given firing rate and a fixed number of jets. Accordingly, a need exists for a method of increasing image resolution without requiring a smaller dot size or a faster print head jet firing rate, and without increasing print time.